Abstract:
:The UV photodissociation kinetics of tryptophan amino acid, Trp, attached to the membrane of bacteria, Escherichia coli and Bacillus subtilis, have been studied by means of normal and synchronous fluorescence. Our experimental data suggest that the fluorescence intensity of Trp increases during the first minute of irradiation with 250 nm to ∼ 280 nm, 7 mW/cm2 UV light, and subsequently decreases with continuous irradiation. During this short, less than a minute, period of time, 70% of the 107 cell per milliliter bacteria are inactivated. This increase in fluorescence intensity is not observed when tryptophan is in the free state, namely, not attached to a protein, but dissolved in water or saline solution. This increase in fluorescence is attributed to the additional fluorescence of tryptophan molecules formed by protein unfolding, the breakage of the bond that attaches Trp to the bacterial protein membrane, or possibly caused by the irradiation of 2 types of tryptophan residues that photolyze with different quantum yields.
journal_name
Proc Natl Acad Sci U S Aauthors
Li R,Dhankhar D,Chen J,Cesario TC,Rentzepis PMdoi
10.1073/pnas.1909722116subject
Has Abstractpub_date
2019-09-17 00:00:00pages
18822-18826issue
38eissn
0027-8424issn
1091-6490pii
1909722116journal_volume
116pub_type
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